The present invention relates to a constant velocity universal joint for use in power transmission devices in motor vehicles and various industrial machines. In particular, the invention relates to a tripod type constant velocity universal joint.
Tripod type constant velocity universal joints are used, for example, as an element in a power transmission device for transmitting rotational power from a car engine to wheels (as a joint for coupling drive shafts or propeller shafts).
In general, a tripod type constant velocity universal joint is chiefly composed of an outer joint member and a tripod member. The outer joint member has an inner periphery provided with three track grooves, each of which has axial roller guideways on both sides. The tripod member has three radially-projecting trunnions. A roller is rotatably arranged on each of the trunnions. The trunnions of the tripod member and the roller guideways in the outer joint member engage with each other in the direction of rotation via the rollers so that rotational torque is transmitted from a drive side to a driven side at constant velocity. The individual rollers rotate about the trunnions and roll on the roller guideways as well, absorbing relative axial displacements and angular displacements between the outer joint member and the tripod member. In the meantime, also absorbed are axial displacements of the individual trunnions to the roller guideways, the axial displacements resulting from phase changes in the direction of rotation when the outer joint member and the tripod member transmit rotational torque with some operating angle therebetween.
Among factors contributing to the vibration characteristics of a constant velocity universal joint of this type are induced thrust and slide resistance. The induced thrust is a periodic varying force produced by friction between internal parts of the constant velocity universal joint when the joint transmits rotational torque with an operating angle. That is, due to the rotational motion, the individual trunnions of the tripod member and the rollers inevitably repeat relative axial reciprocation to the roller guideways. In that case, friction occurs at such portions as between the rollers and the roller guideways, and between the rollers and the trunnions. This friction produces the induced thrust. Thus, the induced thrust is a varying force inherent in a constant velocity universal joint, inevitably occurring in relation to the internal structure and rotational motion of the joint. In the case of a tripod type constant velocity universal joint, the induced thrust consists chiefly of a variation component of third order (tertiary rotational component) because the numbers of trunnions and rollers are three. Meanwhile, the slide resistance is a periodic varying force produced by friction between the internal parts when external vibrations are input to the constant velocity universal joint under torque. In other words, the slide resistance indicates the vibration transfer characteristics of the constant velocity universal joint.
For the power transmission device of a motor vehicle, the vibrations resulting from the induced thrust and slide resistance of the constant velocity universal joint are rather small in level as compared with engine vibrations and the like, and thus matter little by themselves. Nevertheless, the vibrations, if approaching the engine vibrations and the like in frequency, cause resonance phenomena. The induced thrust causes the rolling of a car body at starts and under acceleration, as well as muffled noise, beat noise, and so on. The slide resistance causes an increase of idling vibrations and the like (in particular, affecting the D-range idling vibrations). Accordingly, the induced thrust and slide resistance in the constant velocity universal joint have significant influence on the NVH (noise vibration harshness) performances of the motor vehicle. In particular, the induced thrust is ever increasing in the degree of influence on the NVH performances, with widening regular-use angles (vehicle-mounted angles) of the joint and increasing torque in recent times. Then, in terms of vehicle design, it means that the values of the induced thrust and slide resistance of constant velocity universal joints constitute greater constraints on the layout design of power transmission systems.
An object of the present invention is to regulate the induced thrust and slide resistance of a constant velocity universal joint, thereby easing the constraints on the layout design of a power transmission system and providing a constant velocity universal joint of low vibration and high reliability in quality.
Another object of the present invention is to further reduce and stabilize the induced thrust and slide resistance of a constant velocity universal joint, and then provide a constant velocity universal joint that is excellent in durability, productivity, and strength, low in vibration, and compact in size.
To achieve the foregoing objects, the present invention provides a constant velocity universal joint including: an outer joint member having three track grooves formed in its inner periphery, each of the track grooves having axial roller guideways on both sides; a tripod member having three radially-projecting trunnions; and rollers respectively arranged on the trunnions of the tripod member, the rollers being guided by the roller guideways. Here, at least either induced thrust or slide resistance is regulated within a specification. This increases the reliability as to the induced thrust and/or slide resistance of the constant velocity universal joint, thereby easing the constraints on the layout design of the power transmission system and improving the design flexibility. The constant velocity universal joint also improves in vehicle mountability. Moreover, the reliability as to the vibration characteristics of the constant velocity universal joint increases to contribute to stabilized NVH performances of a vehicle.
Specifically, the number of revolutions R=100-500 (rpm) and an operating angle xcex8=0-14 (deg) are employed as common conditions. Then, under load torque T=0.1xc3x97Ts (Nxc2x7m) {condition (X1)}, the tertiary rotational component of the induced thrust may be regulated to or below 30 N (RMS: Root Mean Square), or preferably to or below 20 N (RMS). Under load torque T=0.2xc3x97Ts (Nxc2x7m) {condition (X2)}, the tertiary rotational component of the induced thrust may be regulated to or below 55 N (RMS), or preferably to or below 35 N (RMS) Under load torque T=0.3xc3x97Ts (Nxc2x7m) {condition (X3)}, the tertiary rotational component of the induced thrust may be regulated to or below 80 N (RMS), or preferably to or below 55 N (RMS). These regulations allow the provision of a constant velocity universal joint of low vibration and high quality reliability, aside from the effects described above. They also contribute to improved NVH performances of a motor vehicle.
Furthermore, with the number of revolutions R=0 (rpm), an operating angle xcex8=0-10 (deg), load torque T=98-196 (Nxc2x7m), and a vibrating frequency f=15-40 (Hz) as common conditions, the slide resistance may be regulated to or below 40 N (peak to peak) under vibrating amplitude=xc2x10.01 to xc2x10.03 (mm) {condition (Y1)}. Under vibrating amplitude=xc2x10.05 to xc2x10.08 (mm) {condition (Y2)}, the slide resistance may be regulated to or below 60 N (peak to peak). Under vibrating amplitude=xc2x10.10 to xc2x10.25 (mm) {condition (Y3)}, the slide resistance may be regulated to or below 80 N (peak to peak). Here, the xe2x80x9cpeak to peakxe2x80x9d means the total of the absolute values of positive and negative peak values. These regulations allow the provision of a constant velocity universal joint of low vibration and high quality reliability, aside from the effects described above. They also contribute to improved NVH performances of a motor vehicle.
In the configurations described above, it is preferable to provide roller assemblies for allowing tilting movements of the rollers with respect to the trunnions. These roller assemblies may include the rollers and support rings for supporting the rollers rotatably, the support rings being fitted onto the outer peripheries of the trunnions. Here, the inner peripheries of the support rings have an arcuate convex section. The outer peripheries of the trunnions are straight in a longitudinal section, and so shaped in a cross section as to make contact with the inner peripheries of the support rings in directions perpendicular to the axis of the joint and create clearances with the inner peripheries of the support rings in the axial direction of the joint. In this configuration, the roller assemblies that include the rollers and the support rings make unitary tilting movements with respect to the trunnions. Here, the term xe2x80x9ctilting movementsxe2x80x9d refers to the tilts the axes of the support rings and rollers make with respect to the axes of the trunnions, within the planes containing the axes of the trunnions.
The cross-sectional shape of such a trunnion as makes contact with the inner periphery of a support ring in a direction perpendicular to the axis of the joint and creates a clearance with the inner periphery of the support ring in an axial direction of the joint translates into that the faces opposed to each other in the axial direction of the tripod member retreat toward each other, i.e., to smaller diameters than the diameter of an imaginary cylindrical surface. Among concrete examples thereof is a generally elliptic shape. The term xe2x80x9cgenerally elliptic shapexe2x80x9d includes not only literal ellipses, but also other shapes generally referred to as ovals and the like.
Due to the change of their cross sections from the conventional circular shape to the shape described above, the trunnions can tilt with respect to the outer joint member without changing the orientation of the roller assemblies when the joint operates with an operating angle. Besides, the contacting ellipses of the support rings with the outer peripheries of the trunnions approach from oblongs to points in shape. This reduces friction moments that act to tilt the roller assemblies. As a result, the roller assemblies are stabilized in orientation, whereby the rollers are retained parallel to the roller guideways for smooth rolling. This means reductions of the induced thrust and slide resistance, accompanied with a narrowed range of variations of these values. Accordingly, in the constant velocity universal joint of this configuration, the specifications of the induced thrust and slide resistance can be made smaller as described above. Besides, these values can be accurately regulated within the specifications. This results in a low-vibration constant velocity universal joint of higher reliability.
The roller assemblies are interposed between the trunnions and the outer joint member for the sake of torque transmission. In constant velocity universal joints of this kind, the transmission direction of torque is always perpendicular to the axis of the joint. Therefore, as long as they make contact in the transmission direction of torque, the trunnions and the support rings can perform torque transmission without trouble even when they have clearances therebetween in the axial directions of the joint.
In the configurations described above, the generator to the inner peripheries of the support rings may consist of a combination of an arc portion at the center and relief portions on both sides. The arc portion preferably has such a radius of curvature as allows 2-3xc2x0 tilts of the trunnions. In addition, a plurality of rolling elements may be interposed between the support rings and the rollers so as to make the support rings and the rollers capable of relative rotations. The rolling elements may be needle rollers. Furthermore, the outer peripheries of the rollers may be formed into a spherical shape (perfect spherical surfaces or torus surfaces) so that the spherical outer peripheries of the rollers and the roller guideways in the outer joint member make angular contact with each other. The angular contact between the rollers and the roller guideways makes the rollers less prone to vibrate, thereby stabilizing the orientation of the rollers. As a result, the rollers can roll on the roller guideways with smaller resistance when moving along the axial direction of the outer joint member. The specific configurations to establish such angular contact include tapered or Gothic arch cross sections of the roller guideways.
The roller assemblies may include the rollers and support rings for supporting the rollers rotatably, the support rings being fitted onto the outer peripheries of the trunnions, wherein the outer peripheries of the trunnions have a convex spherical shape and the inner peripheries of the support rings have a cylindrical or conical shape. In this configuration, the roller assemblies including the rollers and the support rings make unitary tilting movements with respect to the trunnions.
According to this invention, the following effects are obtained.
(1) At least either the induced thrust or the slide resistance is regulated within the specifications, and the reliability as to these characteristics is high. This eases the constraints on the layout design of the power transmission system and improves the design flexibility. Besides, the constant velocity universal joint also improves in vehicle mountability. Moreover, the reliability as to the vibration characteristics of the constant velocity universal joint increases to contribute to stabilized NVH performances of a vehicle.
(2) The tertiary rotational component of the induced thrust is regulated to or below 30 N (RMS) under the condition (X1), to or below 55 N (RMS) under the condition (X2), or to or below 80 N (RMS) under the condition (X3). In addition to the effect (1) described above, these regulations achieve a reduction and stabilization of the induced thrust, thereby making it possible to provide a constant velocity universal joint having excellent low-vibration characteristics and high reliability. This contributes to improved NVH performances of a motor vehicle. Moreover, the constant velocity universal joint becomes capable of regular use at wider angles, which has been difficult, with a further improvement in its vehicle mountability.
(3) Furthermore, the slide resistance is regulated to or below 40 N (peak to peak) under the condition (Y1), to or below 60 N (peak to peak) under the condition (Y2), or to or below 80 N (peak to peak) under the condition (Y3). In addition to the effects (1) and (2) described above, these regulations achieve a reduction and stabilization of the slide resistance, thereby making it possible to provide a constant velocity universal joint having excellent low-vibration characteristics and high reliability. This contributes to improved NVH performances of a motor vehicle.
To achieve the foregoing objects, the present invention also provides a constant velocity universal joint including: an outer joint member having three track grooves each having circumferentially-opposed roller guideways; a tripod member having three radially-projecting trunnions; rollers inserted into the track grooves; and rings fitted onto the trunnions, for supporting the rollers rotatably; the rollers being capable of moving along the roller guideways in the axial direction of the outer joint member. Here, letting TPCD stand for the pitch circle diameter of the track grooves and SPCD for the pitch circle diameter of a spline hole formed in the tripod member, the ratio TPCD/SPCD is set within the range of 1.7-2.1. The ratio of the diameter DJ of the trunnions to the pitch circle diameter SPCD of the spline hole, or DJ/SPCD, is set within the range of 0.6-1.0. The ratio of the diameter DR of the rollers to the pitch circle diameter SPCD of the spline hole, or DR/SPCD, is set within the range of 1.4-2.3.
In a tripod type constant velocity universal joint for use in a motor vehicle""s power transmission system, the pitch circle diameter SPCD of the spline hole in the tripod member is determined by the strength required of the joint. Meanwhile, the outer diameter DO of the outer joint member is limited since the joint must be mounted on a predetermined space in a vehicle. Thus, the individual parts of the constant velocity universal joint need to be put into appropriate dimensional proportions to one another. The ratio TPCD/SPCD defines the pitch circle diameter TPCD of the track grooves. More specifically, if the track grooves are made so small in pitch circle diameter TPCD that the ratio TPCD/SPCD falls below 1.7, there arises a problem of interference between the rollers and the shoulders of the trunnions. Besides, the surface pressures at the contact portions, such as between the trunnions and the rings, increase to cause a drop in durability. On the other hand, if the track grooves are made so large in pitch circle diameter TPCD that the ratio TPCD/SPCD exceeds 2.10, the outer joint member increases in outer diameter DO with deterioration in vehicle mountability. Additionally, given that the outer diameter of the outer joint member is fixed, there remains little space for the roller assemblies.
The ratio DJ/SPCD defines the diameter DJ of the trunnions. More specifically, if the trunnions are made so small in major diameter DJ that the ratio DJ/SPCD falls below 0.6, the constant velocity universal joint cannot function satisfactory. On the other hand, if the trunnions are made so large in major diameter that the ratio DJ/SPCD exceeds 1.0, there remains little space for the roller assemblies to be arranged in, which is dissatisfactory in terms of the limit in the outer diameter.
The ratio DR/SPCD defines the diameter DR of the rollers. More specifically, if the rollers are made so small in outer diameter DR that the ratio DR/SPCD falls below 1.4, the surface pressures between the rollers and the roller guideways increase to drop the durability. Besides, the reduction in the thickness of the rollers causes a problem of deteriorated strength. Meanwhile, when the rollers are made so large in outer diameter DR that the ratio DR/SPCD exceeds 2.3, the outer joint member becomes thinner to drop in forgeability if the diameter DO of the outer joint member is given. This also produces a problem of shaft interference, as well as advances interference of the outer joint member with cup bottoms, yielding an increased cup depth and a greater weight.
In the configuration described above, the rings may be shaped into a spherical cross section while the trunnions are so shaped in a cross section as to make contact with the inner peripheries of the rings in directions perpendicular to the axis of the joint and create clearances with the inner peripheries of the rings in the axial direction of the joint. Besides, the ratio TPCD/SPCD is set within the range of 1.72-2.10. The ratio of the dimension DJL of the trunnions in the directions perpendicular to the axis of the joint to the pitch circle diameter SPCD of the spline hole, or DJL/SPCD, is set within the range of 0.63-0.94. The ratio DR/SPCD is set within the range of 1.47-2.21.
Here, the cross-sectional shape of such a trunnion as makes contact with the inner periphery of a ring in a direction perpendicular to the axis of the joint and creates a clearance with the inner periphery of the ring in an axial direction of the joint translates into that the faces opposed to each other in the axial direction of the tripod member retreat toward each other, i.e., to smaller diameters than the diameter of an imaginary cylindrical surface. Among concrete examples thereof is an ellipse. The term xe2x80x9cellipsexe2x80x9d includes not only literal ellipses, but also other shapes generally referred to as ovals and the like.
Due to the change of their cross sections from the conventional circular shape to the shape described above, the trunnions can tilt with respect to the outer joint member without changing the orientation of the roller assemblies when the joint operates with an operating angle. Besides, the contacting ellipses of the rings with the outer peripheries of the trunnions approach from oblongs to points in shape. This reduces friction moments that act to tilt the roller assemblies. As a result, the roller assemblies are stabilized in orientation, whereby the rollers are retained parallel to the roller guideways for smooth rolling. This contributes to a reduction of the slide resistance, and by extension to the reduction of the induced thrust. There is an additional advantage in that the trunnions improve in flexural strength due to increased section moduli at the bottom portions of the trunnions.
More specifically, the adoption of the cross-sectional shapes of the trunnions as described above eases the contact pressures against the rings and avoids a drop in the strength of the trunnions. Besides, the trunnions can tilt without inclining the rings. This prevents the rollers from inclination and allows the rollers to roll smoothly on the roller guideways. As a result, it becomes possible to omit collars which are sometimes arranged on the track grooves of the outer joint member with an aim to restrain the inclination of the rollers. The omission of the collars not only reduces the outer joint member in weight and simplifies the machining thereto, but also eliminates the slide contacts between the rollers and the collars. This consequently achieves a further decrease of the slide resistance and a reduction of the induced thrust.
The roller assemblies are interposed between the trunnions and the outer joint member for the sake of torque transmission. In constant velocity universal joints of this kind, the transmission direction of torque is always perpendicular to the axis of the joint. Therefore, as long as they make contact in the transmission direction of torque, the trunnions and the support rings can perform torque transmission without trouble even when they have clearances therebetween in the axial directions of the joint.
The numerical ranges of the ratio TPCD/SPCD, the ratio DJL/SPCD, and the ratio DR/SPCD are determined on the bases fundamentally identical to those described above.
Moreover, in the configuration described above, the ratio of the outer diameter DO of the outer joint member to the pitch circle diameter SPCD of the spline hole, or DO/SPCD, may be set within the range of 2.78-3.77. The ratio DO/SPCD defines the diameter DO of the outer joint member. More specifically, if the outer joint member is made so small in outer diameter DO that the ratio DO/SPCD falls below 2.78, the surface pressures at the individual contact portions increase to lower the durability. In addition, the stresses on the individual parts increase to cause deterioration in strength. On the other hand, increasing the outer diameter DO of the outer joint member to such an extent that the ratio DO/SPCD exceeds 3.77 not only deteriorates the vehicle mountability but also yields a weight increase.
Moreover, in the configuration described above, the ratio of the barrel width HT of the tripod member to the pitch circle diameter SPCD of the spline hole, or HT/SPCD, may be set within the range of 0.81-1.22. The ratio HT/SPCD defines the width HT of the tripod member. If the tripod member is made so small in width HT that the ratio HT/SPCD falls below 0.81, the length of the spline fit decreases to lower the spline strength. On the other hand, if the tripod member is made so large in width HT that the ratio HT/SPCD exceeds 1.22, there arises a problem of interference between the rollers and the shoulders of the trunnions.
Moreover, in the configuration described above, the ratio of the width HR of the rollers to the pitch circle diameter SPCD of the spline hole, or HR/SPCD, may be set within the range of 0.38-0.67. The ratio HR/SPCD defines the width HR of the rollers. More specifically, if the rollers are made so small in width that the ratio HR/SPCD falls below 0.38, the surface pressures between the rollers and the roller guideways increase to drop the durability. Besides, the reduction in the rigidity of the rollers results in insufficient strength. Meanwhile, when the rollers are made so large in width HR that the ratio HR/SPCD exceeds 0.67, the rollers come into interference with the shoulders of the trunnions. Moreover, if the outer diameter of the outer joint member is given, the outer joint member becomes thinner to drop in forgeability.
Moreover, in the configuration described above, the ratio of the radius of curvature RR of the rollers"" outer peripheries to the pitch circle diameter SPCD of the spline hole, or RR/SPCD, may be set within the range of 0.19-1.11. The ratio RR/SPCD defines the radius of curvature RR of the rollers"" outer peripheries. More specifically, if the outer peripheries of the rollers are made so small in the radius of curvature that the ratio RR/SPCD falls below 0.19, the rollers yield drop in rigidity into insufficient strength. Meanwhile, when the outer peripheries of the rollers are made so large in the radius of curvature that the ratio RR/SPCD exceeds 1.11, the outer joint member becomes thinner to drop in forgeability if the diameter DO of the outer joint member is given.
According to this invention, the following effects are obtained.
(1) The dimensions of the individual parts of the constant velocity universal joint are brought into appropriate proportions to one another. Besides, configurations for a constant velocity universal joint with excellent low-vibration characteristics are provided.
(2) In particular, the rings are shaped into a spherical cross section while the trunnions are so shaped in a cross section as to make contact with the inner peripheries of the rings in directions perpendicular to the axis of the joint and create clearances with the inner peripheries of the rings in the axial direction of the joint. This allows the trunnions to tilt with respect to the outer joint member without changing the orientation of the roller assemblies when the joint operates with an operating angle. Besides, the contacting ellipses of the rings with the outer peripheries of the trunnions approach from oblongs to points in shape, which reduces friction moments that act to tilt the roller assemblies. In addition, the contacts between the trunnions and the inner peripheries of the rings always stay at the width centers of the rings. Therefore, even when rolling elements such as needle rollers are interposed between the rings and the rollers, these rolling elements make stable rolling. As a result, the roller assemblies are stabilized in orientation, whereby the rollers are retained parallel to the roller guideways for smooth rolling. This contributes to a reduction of the slide resistance, and by extension to the reduction of the induced thrust. There is an additional advantage in that the trunnions improve in flexural strength due to increased section moduli at the bottom portions of the trunnions.
(3) The constant velocity universal joints of the present invention, when applied to a motor vehicle""s drive shaft in particular, can contribute to improvements in automotive NVH performances associated with the slide resistance and induced thrust, thereby increasing design flexibility of portions around the axles of the vehicle.
Now, with an eye to yet an effective reduction and the stabilization of the induced thrust and slide resistance, the following considerations can be made.
From among the constant velocity universal joints of the present invention having been described, take, for example, the one in which: the inner peripheries of the support rings have an arcuate convex section; and the outer peripheries of the trunnions are straight in a longitudinal section, and so shaped in a cross section as to make contact with the inner peripheries of the support rings in directions perpendicular to the axis of the joint and create clearances with the inner peripheries of the support rings in the axial direction of the joint. As exaggeratedly shown in FIG. 26, slight radial clearances exist between the parts constituting each roller assembly A (between the roller 34 and the needle rollers 36, between the support ring 32 and the needle rollers 36), between the roller 34 and the roller guideway 14, and between the support ring 32 and the trunnion 22 when the joint is put under no load. Therefore, as exaggeratedly shown in FIG. 27, when a load is applied to among the trunnion 22, the roller assembly A, and the roller guideway 14 to reduce the clearances mentioned above in rotational torque transmission, the axis X of the trunnion 22 tilts with respect to the axis Y of the roller assembly A by the amount corresponding to the clearances mentioned above (tilt angle xcex2) within the plane of the diagram (within a section perpendicular to the axis of the joint). This tilt of the trunnion 22 deviates the direction of the load F applied to the contact portion S between the trunnion 22 and the roller assembly A (the contact point between the outer periphery 22a of the trunnion 22 and the inner periphery 32c of the support ring 32) from the direction of torque transmission (the direction of the tangent at the contact point S to a circle about the joint center O) to an inward direction. This produces a component of force f directed to the trunnion bottom (hereinafter, this component of force will be referred to as xe2x80x9cinward component fxe2x80x9d). Moreover, the support ring 32 and the lock rings 33, 35 also have slight axial clearances therebetween, so that the support ring 32 can make an axial relative shift with respect to the roller 34 by the amount corresponding to the axial clearances. Thus, when the above-described inward component f is applied, the support ring 32 makes a relative shift toward the trunnion bottom and comes into contact with the lock ring 35. Accordingly, the center line L1 passing through the center of curvature of the inner periphery 32s of the support ring 32 makes a xcex94h shift toward the trunnion bottom from the center line L2 passing through the center of curvature of the outer periphery 34a of the roller 34. This consequently promotes the inward component f in magnitude. Then, due to such an inward component f, the roller assembly A makes a clockwise tilt within the plane of the diagram, with respect to the roller guideway 14. This increases the chances for the outer periphery 34a of the roller 34 to contact with the trunnion-bottom side of the roller guideway 14 in the non-load direction (not shown). Therefore, the smooth rolling of the roller 34 is sometimes hampered to affect the induced thrust and slide resistance of the joint.
In view of the foregoing considerations, the present invention provides a constant velocity universal joint including: an outer joint member having three axial track grooves formed in its inner periphery, each of the track grooves having axial roller guideways on both sides; a tripod member having three radially-projecting trunnions; and roller assemblies respectively mounted on the trunnions of the tripod member; the roller assemblies including rollers to be guided along the roller guideways in directions parallel to the axis of the outer joint member and support rings for supporting the rollers rotatably, the roller assemblies being capable of tilting movements with respect to the trunnions. Here, the constant velocity universal joint further includes tilt suppressing means for suppressing tilts of the roller assemblies within a cross section perpendicular to the axis of the joint due to inward components of load applied to contact portions between the trunnions and the roller assemblies. Here, the term xe2x80x9cinward componentsxe2x80x9d refers to components of loads toward the trunnion bottoms, resulting from an inward deviation of the loads applied to the contact portions between the trunnions and the roller assemblies from the direction of torque transmission.
For the tilt suppression means mentioned above, a configuration may be adopted in which two-point angular contact is established between the outer peripheries of the rollers and the roller guideways, and the contact angle at angular contact points on the trunnion-bottom sides is made greater than the contact angle at angular contact points on the trunnion-extremity sides. According to this configuration, the angular contact between the rollers and the roller guideways stabilizes the orientation of the rollers with respect to the roller guideways. In addition, since the contact angle at the angular contact points on the trunnion-bottom sides is made greater than the contact angle at the angular contact points on the trunnion-extremity sides, the inward components can be exerted higher at the angular contact points on the trunnion-bottom sides. Accordingly, the tilts of the roller assembly within a section perpendicular to the axis of the joint are suppressed to ensure smooth rolling of the rollers. Incidentally, the roller guideways may be shaped to Gothic arch, tapered (V-shaped), or parabolic cross sections so as to achieve the angular contact.
Moreover, the tilt suppressing means may adopt a configuration in which the outer peripheries of the rollers are shaped into arcuate convex sections having the centers of curvature in the vicinities of lines parallel to the axes of the rollers, the lines passing through the contact portions. According to this configuration, the above-mentioned contact portions, or the points of application of the inward components, and the centers of curvature of the outer peripheries of the rollers, or the fulcrums of the tilts of the roller assemblies, are brought near to or coincident with each other in the radial directions of the roller assemblies. This reduces the tilting moments acting on the roller assemblies. Therefore, the tilts of the roller assemblies within a section perpendicular to the axis of the joint are suppressed to ensure the smooth rolling of the rollers.
The above-described constant velocity universal joint may employ such a configuration as includes the rollers to be guided by roller guideway and support rings for supporting the rollers rotatably, wherein: the inner peripheries of the support rings have an arcuate convex section; and the outer peripheries of the trunnions are straight in a longitudinal section, and so shaped in a cross section as to make contact with the inner peripheries of the support rings in directions perpendicular to the axis of the joint and create clearances with the inner peripheries of the support rings in the axial direction of the joint.
The cross-sectional shape of such a trunnion as makes contact with the inner periphery of a support ring in a direction perpendicular to the axis of the joint and creates a clearance with the inner periphery of the support ring in an axial direction of the joint translates into that the faces opposed to each other in the axial direction of the tripod member retreat toward each other, i.e., to smaller diameters than the diameter of an imaginary cylindrical surface. Among concrete examples thereof is a generally elliptic shape. The term xe2x80x9cgenerally elliptic shapexe2x80x9d includes not only literal ellipses, but also other shapes generally referred to as ovals and the like.
Due to the change of their cross sections from the conventional circular shape to the shape described above, the trunnions can tilt with respect to the outer joint member without changing the orientation of the roller assemblies (roller assemblies) when the joint operates with an operating angle. Besides, the contacting ellipses of the support rings with the outer peripheries of the trunnions approach from oblongs to points in shape. This reduces friction moments that act to tilt the roller assemblies. As a result, the roller assemblies are stabilized in orientation, whereby the rollers are retained parallel to the roller guideways for smooth rolling. This contributes to a reduction of the slide resistance, and by extension to the reduction of the induced thrust.
In the configuration described above, the generator to the inner peripheries of the support rings may consist of a combination of an arc portion at the center and relief portions on both sides. The arc portion preferably has such a radius of curvature as allows 2-3xc2x0 tilts of the trunnions.
In the constant velocity universal joint of the above-described configuration, axial relative movements of the rollers and the support rings can be retained from both sides by lock means such as lock rings and lock collars, so as to ensure the unity of the roller assemblies as assemblies. Nevertheless, axial clearances must be secured between the rollers/support rings and the lock means. Then, the support rings are still capable of axial relative movements to the rollers by the amounts corresponding to the axial clearances. Therefore, when the above-described inward components are applied, the support rings make relative movements toward the trunnion bottoms, with respect to the rollers. Accordingly, the center lines passing through the centers of curvature of the inner peripheries of the support rings make a shift toward the trunnion bottoms, from the center lines passing through the centers of curvature of the outer peripheries of the rollers. As a result, the inward components are promoted in magnitude. To prevent this, the above-described tilt suppressing means may adopt such a configuration as establishes coincidence between the center lines passing through the respective centers of curvature of the outer peripheries of the rollers and the center lines passing through the respective centers of curvature of the inner peripheries of the support rings when the support rings make relative movements to the trunnion bottoms with respect to the rollers due to clearances between parts that constitute the roller assemblies. This configuration reduces the above-described inward components. As a result, the tilts of the roller assemblies within a section perpendicular to the axis of the joint are suppressed to ensure the smooth rolling of the rollers.
Moreover, the above-mentioned tilt suppressing means may include the outer peripheries of the trunnions, inclined so as to spread out toward the trunnion bottoms in their longitudinal sections. According to this configuration, even when the axes of the trunnions tilt with respect to the axes of the roller assembly within the section perpendicular to the axis of the joint, the tilts of the outer peripheries of the trunnions in themselves are suppressed or cancelled out. This reduces the above-described inward components. As a result, the tilts of the roller assemblies within the section perpendicular to the axis of the joint are suppressed to ensure the smooth rolling of the rollers.
Any of the specific configurations of the tilt suppressing means described above may be employed by itself. Two or more configurations may be used in combination.
In the configurations described above, a plurality of rolling elements may be interposed between the support rings and the rollers so as to make the support rings and the rollers capable of relative rotations. The rolling elements may be needle rollers, balls, and the like.
According to this invention, the tilts of the roller assemblies resulting from the inward components of loads applied to the contact portions between the trunnions and the roller assemblies are suppressed to achieve more effective reduction and stabilization of the induced thrust and slide resistance in a joint. This makes it possible to provide a tripod type constant velocity universal joint of yet lower vibration.
The nature, principle, and utility of the invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings in which like parts are designated by like reference numerals or characters.